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(_nss_dns_getcanonname_r): Don't use CNAME records, we better follow the chain of CNAME records which can be accomplished with A/AAAA lookups.

This commit is contained in:
Ulrich Drepper 2004-08-16 17:13:13 +00:00
parent a29db458e3
commit 3207d4364e
1 changed files with 85 additions and 69 deletions
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154
resolv/nss_dns/dns-canon.c
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@ -53,81 +53,97 @@ _nss_dns_getcanonname_r (const char *name, char *buffer, size_t buflen,
unsigned char *ptr;
} ansp = { .ptr = buf };
enum nss_status status;
int qtypes[] = { ns_t_a, ns_t_aaaa };
#define nqtypes (sizeof (qtypes) / sizeof (qtypes[0]))
int r = __libc_res_nquery (&_res, name, ns_c_in, ns_t_cname,
buf, sizeof (buf), &ansp.ptr);
if (r > 0)
for (int i = 0; i < nqtypes; ++i)
{
/* We need to decode the response. Just one question record.
And if we got no answers we bail out, too. */
if (ansp.buf->hdr.qdcount != htons (1)
|| ansp.buf->hdr.ancount == 0)
goto unavail;
/* Beginning and end of the buffer with query, answer, and the
rest. */
unsigned char *ptr = &ansp.buf->buf[sizeof (HEADER)];
unsigned char *endptr = ansp.ptr + r;
/* Skip over the query. This is the name, type, and class. */
int s = __dn_skipname (ptr, endptr);
if (s < 0)
goto unavail;
/* Skip over the name and the two 16-bit values containing type
and class. */
ptr += s + 2 * sizeof (uint16_t);
/* Now the reply. First again the name from the query, then
type, class, TTL, and the length of the RDATA. */
s = __dn_skipname (ptr, endptr);
if (s < 0)
goto unavail;
ptr += s;
/* Check whether type and class match. */
if (*(uint16_t *) ptr != htons (ns_t_cname))
goto unavail;
ptr += sizeof (uint16_t);
if (*(uint16_t *) ptr != htons (ns_c_in))
goto unavail;
/* Also skip over the TTL and rdata length. */
ptr += sizeof (uint16_t) + sizeof (uint32_t) + sizeof (int16_t);
/* Now the name we are looking for. */
s = __dn_expand (ansp.buf->buf, endptr, ptr, buffer, buflen);
if (s < 0)
int r = __libc_res_nquery (&_res, name, ns_c_in, qtypes[i],
buf, sizeof (buf), &ansp.ptr);
if (r > 0)
{
if (errno != EMSGSIZE)
goto unavail;
/* We need to decode the response. Just one question record.
And if we got no answers we bail out, too. */
if (ansp.buf->hdr.qdcount != htons (1))
continue;
/* The buffer is too small. */
*errnop = ERANGE;
status = NSS_STATUS_TRYAGAIN;
h_errno = NETDB_INTERNAL;
}
else
{
/* Success. */
*result = buffer;
status = NSS_STATUS_SUCCESS;
/* Number of answers. */
unsigned int ancount = ntohs (ansp.buf->hdr.ancount);
/* Beginning and end of the buffer with query, answer, and the
rest. */
unsigned char *ptr = &ansp.buf->buf[sizeof (HEADER)];
unsigned char *endptr = ansp.ptr + r;
/* Skip over the query. This is the name, type, and class. */
int s = __dn_skipname (ptr, endptr);
if (s < 0)
{
unavail:
status = NSS_STATUS_UNAVAIL;
break;
}
/* Skip over the name and the two 16-bit values containing type
and class. */
ptr += s + 2 * sizeof (uint16_t);
while (ancount-- > 0)
{
/* Now the reply. First again the name from the query,
then type, class, TTL, and the length of the RDATA.
We remember the name start. */
unsigned char *namestart = ptr;
s = __dn_skipname (ptr, endptr);
if (s < 0)
goto unavail;
ptr += s;
/* Check whether type and class match. */
unsigned int type = ntohs (*(uint16_t *) ptr);
if (type == qtypes[i])
{
/* We found the record. */
s = __dn_expand (ansp.buf->buf, endptr, namestart,
buffer, buflen);
if (s < 0)
{
if (errno != EMSGSIZE)
goto unavail;
/* The buffer is too small. */
*errnop = ERANGE;
status = NSS_STATUS_TRYAGAIN;
h_errno = NETDB_INTERNAL;
}
else
{
/* Success. */
*result = buffer;
status = NSS_STATUS_SUCCESS;
}
goto out;
}
if (type != ns_t_cname)
goto unavail;
ptr += sizeof (uint16_t);
if (*(uint16_t *) ptr != htons (ns_c_in))
goto unavail;
/* Also skip over the TTL. */
ptr += sizeof (uint16_t) + sizeof (uint32_t);
/* Skip over the data length and data. */
ptr += sizeof (uint16_t) + ntohs (*(uint16_t *) ptr);
}
}
}
else if (h_errno == TRY_AGAIN)
{
again:
status = NSS_STATUS_TRYAGAIN;
*errnop = errno;
}
else
{
unavail:
status = NSS_STATUS_UNAVAIL;
*errnop = errno;
}
out:
*h_errnop = h_errno;
if (ansp.ptr != buf)